Metallized film-over-foam contacts

ABSTRACT

A contact suitable for circuit grounding of surface mount technology devices generally includes a resilient core member, a solderable electrically conductive layer, and an adhesive bonding the solderable electrically conductive layer to the resilient core member. The adhesive has no more than a maximum of 900 parts per million chlorine, no more than a maximum of 900 parts per million bromine, and no more than a maximum of 1,500 parts per million total halogens.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/219,104 filed Mar. 19, 2014 (published as 2014/0203069 on Jul. 24,2014, to issue as U.S. Pat. No. 9,131,616 on Sep. 8, 2015), which, inturn, was a continuation-in-part of PCT International Application No.PCT/US2013/051350 filed Jul. 19, 2013 (published as WO 2014/022125 onFeb. 6, 2014), which claimed the benefit of U.S. Provisional ApplicationNo. 61/676,927 filed Jul. 28, 2012. The entire disclosures of each ofthese applications are incorporated herein by reference.

FIELD

The present disclosure generally relates to contacts (e.g., metallizedfilm-over-foam contacts, etc.) that can be surface mounted (e.g.,soldered, etc.) to desired surfaces in association with surface mounttechnologies to establish electrical contact between the desiredsurfaces and the contacts, and that can be used for grounding purposesand/or shielding purposes, and that are also formed from environmentallyfriendly materials (e.g., halogen-free flame or fire retardants, etc.)and/or are capable of achieving desired flame ratings according toUnderwriters Laboratories Standard No. 94 such as, for example,Horizontal Burn (HB), and Vertical Burn V-1, V-2, and preferably V-0,etc.

BACKGROUND

This section provides background information related to the presentdisclosure which is not necessarily prior art.

Printed circuit boards (PCBs) usually include electrical components thatradiate electromagnetic waves, which may cause noise or unwanted signalsto appear in electrical devices existing within a certain proximity ofthe radiating electrical components. Accordingly, it is not uncommon toprovide grounding for circuitry that emits or is susceptible toelectromagnetic radiation, to thereby allow offending electrical chargesand fields to be dissipated without disrupting operation.

To accomplish this grounding, some printed circuit boards are providedwith pem-type standoffs. Additional grounding solutions may includecustomized gaskets that are designed specifically for the particularapplication. In such applications, the custom design usually depends,for example, on the exact printed circuit board layout andconfiguration. Other grounding solutions require through holes onmulti-layered boards, which may entail re-routing hundreds of groundtraces. Plus, the need for additional grounding contacts frequentlyarises later during the PCB layout. Other example grounding solutionsinclude metal spring-finger contacts or hard fasteners using nuts.

SUMMARY

This section provides a general summary of the disclosure, and is not acomprehensive disclosure of its full scope or all of its features.

Example embodiments of contacts (e.g., gaskets, etc.) are providedherein. In one example embodiment, a metallized film-over-foam contactsuitable for circuit grounding of surface mount technology devicesgenerally includes a resilient core member, a solderable electricallyconductive layer, and an adhesive bonding the solderable electricallyconductive layer to the resilient core member. The adhesive has no morethan a maximum of 900 parts per million chlorine, no more than a maximumof 900 parts per million bromine, and no more than a maximum of 1,500parts per million total halogens.

In some aspects, the contact may have a flame rating of V-0 underUnderwriter's Laboratories (UL) Standard No. 94. In some aspects, thecontact may have a flame rating of V-1 under Underwriter's Laboratories(UL) Standard No. 94. In some aspects, the contact may have a flamerating of V-2 under Underwriter's Laboratories (UL) Standard No. 94. Insome aspects, the contact may have a flame rating of HB underUnderwriter's Laboratories (UL) Standard No. 94.

In some aspects, the resilient core member of the contact may includesilicone foam, and the solderable electrically conductive layer mayinclude a metallized film comprising copper and tin. And, in someaspects, the resilient core member may have a density of about 5 poundsper cubic foot or more (or about 10 pounds per cubic foot or more, orabout 15 pounds per cubic foot or more). In some aspects, the solderableelectrically conductive layer may include a polyimide film comprising alayer of copper and a layer of tin, and the layer of copper may beformed on the polyimide film and the layer of tin may be formed over thelayer of copper. In other aspects, the resilient core member of thecontact may include urethane foam, etc.

In some aspects, the contact may have a surface resistance of less thanabout 0.07 ohms per square. In some aspects, the contact may be reflowtunnel compatible to about 245 degrees Celsius. In some aspects, thecontact may include a pressure sensitive adhesive coupled to at leastpart of the solderable electrically conductive layer, and configured tocouple the contact to a surface of a printed circuit board. In someaspects, the contact may have a generally hourglass cross-sectionalshape.

In some aspects, the resilient core member of the contact may have nomore than a maximum of 900 parts per million chlorine, no more than amaximum of 900 parts per million bromine, and no more than a maximum of1,500 parts per million total halogens; and/or the solderableelectrically conductive layer of the contact may have no more than amaximum of 900 parts per million chlorine, no more than a maximum of 900parts per million bromine, and no more than a maximum of 1,500 parts permillion total halogens. In some aspects, the contact may have no morethan a maximum of 900 parts per million chlorine, no more than a maximumof 900 parts per million bromine, and no more than a maximum of 1,500parts per million total halogens. In some aspects, the contact may haveno more than a maximum of 50 parts per million chlorine and no more thana maximum of 50 parts per million bromine. In some aspects, theresilient core member, the solderable electrically conductive layer,and/or the adhesive of the contact may be entirely free of halogen. Insome aspects, the contact may be free of red phosphorus flame retardantand/or expandable carbon graphite and/or antimony. In some aspects, thecontact may include no more than a maximum of about 1,000 parts permillion of antimony. In some aspects, the resilient core member of thecontact may be free of flame retardant added thereto.

In some aspects, the contact may consist of only three layers, includinga first layer defined solely by the resilient core member, a secondlayer defined solely by the adhesive, and a third layer defined solelyby the solderable electrically conductive layer. As such, the contactmay consist of only the resilient core member, the adhesive, and thesolderable electrically conductive layer.

In another example embodiment, a halogen-free metallized film-over-foamcontact suitable for circuit grounding of surface mount technologydevices generally includes a resilient core member, a metal compositionfilm, and an adhesive bonding the metal composition film to theresilient core member. The resilient core member is free of flameretardant added thereto. And, the resilient core member, the metalcomposition film, and the adhesive combined have no more than a maximumof 900 parts per million chlorine, no more than a maximum of 900 partsper million bromine, and no more than a maximum of 1,500 parts permillion total halogens such that the contact is halogen free.

In some aspects, the contact may have a flame rating of V-0 underUnderwriter's Laboratories (UL) Standard No. 94. In some aspects, thecontact may have a flame rating of V-1 under Underwriter's Laboratories(UL) Standard No. 94. In some aspects, the contact may have a flamerating of V-2 under Underwriter's Laboratories (UL) Standard No. 94. Insome aspects, the contact may have a flame rating of HB underUnderwriter's Laboratories (UL) Standard No. 94.

In some aspects, the contact may have a surface resistance of less thanabout 0.07 ohms per square. In some aspects, the contact may be reflowtunnel compatible to about 245 degrees Celsius. In some aspects, thecontact may include a pressure sensitive adhesive coupled to at leastpart of the solderable electrically conductive layer, and configured tocouple the contact to a surface of a printed circuit board. In someaspects, the contact may have a generally hourglass cross-sectionalshape.

In some aspects, the resilient core member of the contact may includesilicone foam, and the solderable electrically conductive layer mayinclude a metallized film comprising copper and tin. And, in someaspects, the resilient core member may have a density of about 5 poundsper cubic foot or more (or about 10 pounds per cubic foot or more, orabout 15 pounds per cubic foot or more). In some aspects, the solderableelectrically conductive layer may include a polyimide film comprising alayer of copper and a layer of tin, and the layer of copper may beformed on the polyimide film and the layer of tin may be formed over thelayer of copper. In other aspects, the resilient core member of thecontact may include urethane foam, etc.

In some aspects, the resilient core member of the contact may have nomore than a maximum of 900 parts per million chlorine, no more than amaximum of 900 parts per million bromine, and no more than a maximum of1,500 parts per million total halogens; and/or the solderableelectrically conductive layer of the contact may have no more than amaximum of 900 parts per million chlorine, no more than a maximum of 900parts per million bromine, and no more than a maximum of 1,500 parts permillion total halogens. In some aspects, the contact may have no morethan a maximum of 900 parts per million chlorine, no more than a maximumof 900 parts per million bromine, and no more than a maximum of 1,500parts per million total halogens. In some aspects, the contact may haveno more than a maximum of 50 parts per million chlorine and no more thana maximum of 50 parts per million bromine. In some aspects, theresilient core member, the solderable electrically conductive layer,and/or the adhesive of the contact may be entirely free of halogen. Insome aspects, the contact may be free of red phosphorus flame retardantand/or expandable carbon graphite and/or antimony. In some aspects, thecontact may include no more than a maximum of about 1,000 parts permillion of antimony. In some aspects, the resilient core member of thecontact may be free of flame retardant.

In some aspects, the contact may consist of only three layers, includinga first layer defined solely by the resilient core member, a secondlayer defined solely by the adhesive, and a third layer defined solelyby the solderable electrically conductive layer. As such, the contactmay consist of only the resilient core member, the adhesive, and thesolderable electrically conductive layer.

In another example embodiment, a method of installing a halogen freemetallized film-over-foam contact to a surface of a printed circuitboard generally includes soldering an electrically conductive layer ofthe halogen free contact to a surface of a printed circuit board,whereby an electrical pathway is established from the printed circuitboard to the contact through the electrically conductive layer.

In some aspects, the contact includes a silicone foam core and theelectrically conductive layer includes a metalized film. Here, themetalized film may surround at least part of the silicone foam core.And, in some aspects, the resilient core member may have a density ofabout 5 pounds per cubic foot or more (or about 10 pounds per cubic footor more, or about 15 pounds per cubic foot or more).

In some aspects, the method may also include placing the contact using asurface mount technology machine onto a ground trace of the printedcircuit board, where the ground trace is pre-screened with solder paste.In some aspects, the method may also include performing a solder reflowoperation while the contact is on the solder paste to thereby solder thecontact to the ground trace of the printed circuit board.

In some aspects, the contact may have a flame rating of V-0 underUnderwriter's Laboratories (UL) Standard No. 94. In some aspects, thecontact may have a flame rating of V-1 under Underwriter's Laboratories(UL) Standard No. 94. In some aspects, the contact may have a flamerating of V-2 under Underwriter's Laboratories (UL) Standard No. 94. Insome aspects, the contact may have a flame rating of HB underUnderwriter's Laboratories (UL) Standard No. 94.

Further areas of applicability will become apparent from the descriptionprovided herein. The description and specific examples in this summaryare intended for purposes of illustration only and are not intended tolimit the scope of the present disclosure.

DRAWINGS

The drawings described herein are for illustrative purposes only ofselected embodiments and not all possible implementations, and are notintended to limit the scope of the present disclosure.

FIG. 1 is a front elevation view of a contact according to an exampleembodiment of the present disclosure;

FIG. 2 is a perspective view of the contact of FIG. 1;

FIG. 3 is a front elevation view of the contact of FIG. 1 shown surfacemounted, via solder paste, to a solder pad of a printed circuit board;

FIG. 4 illustrates example reflow conditions for a reflow solderingoperation suitable for coupling the contact of FIG. 3 to the printedcircuit board;

FIG. 5 is a front elevation view of a contact according to anotherexample embodiment of the present disclosure;

FIG. 6 is a front elevation view of a contact according to yet anotherexample embodiment of the present disclosure;

FIG. 7 is a perspective view of the contact of FIG. 6;

FIG. 8 is a front elevation view of a contact according to anotherexample embodiment of the present disclosure;

FIG. 9 is a bottom plan view of the contact of FIG. 8;

FIG. 10 is a front elevation view of a contact according to anotherexample embodiment of the present disclosure shown surface mounted, viasolder paste, to a solder pad of a printed circuit board;

FIG. 11 is a front elevation view of another contact according to anexample embodiment of the present disclosure shown surface mounted, viasolder paste, to a solder pad of a printed circuit board;

FIG. 12 is a line graph illustrating resistance (in ohms per inchlength), force (in pounds per inch length), and compression for anexample contact of the present disclosure;

FIG. 13 is a line graph illustrating electrical resistance (in ohms perinch length) and compression force (in pounds per inch length) for twoexample contacts of the present disclosure having the same constructionsbut different shapes, and where the two contacts were each sized with athickness of about 5 millimeters, a width of about 5 millimeters, and alength of about 5 millimeters;

FIG. 14 is a line graph illustrating electrical resistance (in ohms perinch length) and compression force (in pounds per inch length) for twoexample contacts of the present disclosure again having the sameconstructions but different shapes, and where the two contacts were eachsized with a thickness of about 5 millimeters, a width of about 10millimeters, and a length of about 5 millimeters;

FIG. 15 is a line graph illustrating electrical resistance (in ohms perinch length) and compression force (in pounds per inch length) for twoexample contacts of the present disclosure again having the sameconstructions but different shapes, and where the two contacts were eachsized with a thickness of about 10 millimeters, a width of about 10millimeters, and a length of about 10 millimeters; and

FIG. 16 is a line graph illustrating resistance (in ohms per inchlength), force (in pounds per inch length), and percent compression foran example contact of the present disclosure.

Corresponding reference numerals indicate corresponding parts throughoutthe several views of the drawings.

DETAILED DESCRIPTION

Fingerstock gaskets are commonly soldered to printed circuit boards(PCBs) of electronic devices for providing electromagnetic shielding orgrounding. But the inventors hereof have recognized that at least someconventional fingerstock gaskets may be easily fractured.Fabric-over-foam (FOF) gaskets are also used to provide electromagneticshielding or grounding for electronic devices. But the inventors hereofhave recognized that while conventional FOF gaskets tend to have betterelasticity and are less easily fractured than fingerstock gaskets, FOFgaskets are not solderable to PCBs.

After recognizing the above drawbacks, the inventors hereof developedand disclose herein example embodiments of contacts (e.g., gaskets,etc.), configured for use as surface mount devices (SMD) with surfacemount technologies (SMT) (e.g., contacts configured for use as SMDcontacts, etc. and suitable for use in providing grounding and/orshielding functions). For example, the contacts can be surface mountedto surfaces of PCBs by soldering, etc. (e.g., to solder pads of thePCBs, ground traces of the PCBs, etc.). In addition, example embodimentsof the contacts may be formed from environmentally friendly materials(e.g., halogen-free flame or fire retardants, etc.) and/or may haveflame ratings of at least V-0 under the Underwriters LaboratoriesStandard No. 94, “Tests for Flammability of Plastic Materials for Partsin Devices and Appliances” (5^(th) Edition, Oct. 29, 1996). Further,example embodiments of the contacts may retain various advantagesassociated with traditional FOF gaskets (e.g., good elasticity, etc.)and various advantages associated with fingerstock gaskets (e.g.,solderability, etc.), while avoiding the above drawbacks such as theinability of FOF gaskets to be soldered and the relatively easyfracturability of fingerstock gaskets and tendency to cut the fingers ofthose installing the fingerstock.

According to various aspects, there are disclosed herein exampleembodiments of contacts (e.g., metallized film-over-foam contacts, SMDcontacts, metallized film-over-foam SMD contacts, grounding contacts,etc.) suitable for providing grounding and/or shielding functions. Thecontacts generally include resilient cores with electrically conductivelayers positioned, provided, deposited, coated, plated, wrapped, etc.around the resilient cores. And, in various embodiments, theelectrically conductive layers of the contacts are coupled to theresilient cores with adhesives. The contacts can be used in desiredapplications such as, for example, cabinets (e.g., telecommunicationscabinets, etc.) televisions, medical equipment, servers, printers,computers, networking equipment, projectors, etc.

Example embodiments of the contacts can be used as ground circuits ofPCBs, for example, in SMT processes (e.g., as SMD contacts, etc.) forconstructing electronic circuits, etc. In these embodiments, thecontacts are configured to mount to desired surfaces of the PCBs (e.g.,directly to surfaces of the PCBs, to pads coupled to surfaces of thePCBs, etc.) to electrically connect the contacts to the PCBs (e.g., toprovide grounding functions, etc.). To accomplish this, the electricallyconductive layers of the contacts may comprise metallized films thatallow the contacts to be attached, for example, by solder, conductiveadhesives, etc. to the surfaces of the PCBs. The metallized films mayinclude, for example, polymeric films (e.g., polyimide (PI) films, etc.)comprising one or more suitable metals (e.g., copper, tin, aluminum,nickel, silver, palladium aluminum, alloys, combinations thereof, etc.)provided thereto by processes such as plating, sputtering (e.g., filmdeposition, vapor deposition, etc.), combinations thereof, etc.

Example embodiments of the contacts are also able to achieve desiredflame ratings under the Underwriters Laboratories Standard No. 94,“Tests for Flammability of Plastic Materials for Parts in Devices andAppliances” (5^(th) Edition, Oct. 29, 1996) (hereinafter, UL-94). Forexample, some contacts are able to achieve higher flame ratings of V-0.Other contacts are only able to achieve lower flame ratings, such asV-1, V-2, HB, or HF-1. Some example embodiments of the contacts may beable to achieve these desired flame ratings to minimum thicknesses ofthe contacts of at least about 1 millimeter. The desired UL-94 flamerating of the example embodiments of the contacts can depend, forexample, on the particular application or installation for the contacts.

With that said, flame ratings can be determined using UL-94 or using anAmerican Society for Testing and Materials (ASTM) flammability test.UL-94 includes flame ratings of V-0, V-1, V-2, HB, and HF-1, where V-0is a higher flame rating and HF-1 is a lower flame rating. Notably, theV-0 rating is much more difficult to achieve than the V-1, V-2, HB, andHF-1 ratings. A sample product achieving a lower V-1 rating would notnecessarily achieve a higher V-0 rating. Indeed, V-0 and V-1 ratings ofsample products are treated as being mutually exclusive for the sampleproducts and are not overlapping. In other words, a sample productidentified as having a V-1 rating would not also be considered as havinga V-0 rating (otherwise it would be identified as having a V-0 rating).

Under UL-94, flame ratings are determined for a sample product based onburn tests for sets of five specimens of the sample product. Table 1indicates criteria used for determining UL-94 V-0, V-1, V-2 flameratings. For example, to achieve a flame rating of V-0, afterflame time(t₁ or t₂) for each individual specimen of the sample product testedmust be less than or equal to 10 seconds, total afterflame time (t₁ plust₂ for all five specimens) must be less than or equal to 50 seconds, andafterflame plus afterglow time (t₂ plus t₃) for each individual specimenmust be less than or equal to 30 seconds. At the least, each of thesecriteria must be satisfied to achieve a flame rating of V-0. As can beappreciated, the V-0 rating is much more difficult to achieve than theV-1 or V-2 ratings.

TABLE 1 UL-94 CRITERIA CONDITIONS V-0 V-1 V-2 Afterflame time for eachindividual ≦10 s ≦30 s ≦30 s specimen t₁ or t₂ Total afterflame time forany condition ≦50 s ≦250 s  ≦250 s  set (t₁ plus t₂ for the fivespecimens) Afterflame plus afterglow time for each ≦30 s ≦60 s ≦60 sindividual Specimen after the second flame application (t₂ plus t₃)Afterflame or afterglow of any No No No specimen up to the holding clampCotton indicator ignited by flaming No No Yes particles or drops

Further, example embodiments of the contacts are also environmentallyfriendly and may be viewed as halogen-free per InternationalElectrotechnical Commission (IEC) International Standard IEC 61249-2-21(page 15, November 2003, First Edition). International Standard IEC61249-2-21 defines “halogen free” (or free of halogen) for Electricaland Electronic Equipment Covered Under the European Union's Restrictionof Hazardous Substances (RoHS) directive as having no more than amaximum of 900 parts per million chlorine, no more than a maximum of 900parts per million bromine, and no more than a maximum of 1,500 parts permillion total halogens. The phrases “halogen free,” “free of halogen,”and the like are similarly used herein. With that said, in some exampleembodiments the resilient core members, the electrically conductivelayers, or the adhesives of the contacts may each be halogen free. And,in other example embodiments the resilient core members, theelectrically conductive layers, and the adhesives, combined, may behalogen free (such that the contacts are halogen free).

Example embodiments of the contacts will now be described more fullywith reference to the accompanying drawings.

FIGS. 1-4 illustrate an example embodiment of a contact 20 (e.g., a SMDcontact, etc.) suitable for grounding and/or shielding functions andembodying one or more aspects of the present disclosure. As shown, thecontact 20 includes a resilient core member 22, an adhesive 24 (e.g., anepoxy-based adhesive, a hot melt adhesive, a silicone-based adhesive,etc.), and an electrically conductive layer 26. The electricallyconductive layer 26 generally surrounds (e.g., is wrapped about, etc.) aperimeter of the resilient core member 22. And, the adhesive 24(illustrated in an adhesive layer in the figures) bonds the electricallyconductive layer 26 to the resilient core member 22. The illustratedcontact 20 has a generally square cross-sectional shape, with agenerally equal thickness 32 and width 34 (FIG. 1). However, contactscan have other cross-sectional shapes (e.g., rectangular shapes,hourglass shapes, trapezoid shapes, etc.) within the scope of thepresent disclosure. Further, and without limitation, the contact 20 canhave any desired thickness 32 (e.g., 1 millimeter, 3 millimeters, 5millimeters, 13 millimeters, etc.), width 34 (e.g., 1 millimeter, 3millimeters, 5 millimeters, 13 millimeters, etc.), and/or length 36(FIG. 2) within the scope of the present disclosure.

With reference now to FIG. 3, and as previously described, the contact20 can be surface mounted to a surface 42 of a PCB 44 (for electricallycoupling the contact 20 to the PCB 44) and used as a ground circuit ofthe PCB 44, for example, as part of a SMT process for constructing anelectronic circuit, etc. The contact 20 may be placed on the surface 42of the PCB 44 manually or via suitable pick and place equipment (e.g., agripper, a pneumatic head, a vacuum pick-and-place head, a suction cuppick-and-place head, etc.). In the illustrated embodiment, the contact20 is surface mounted (at a generally flat surface 46 of the contact 20)to the PCB 44 via solder and a reflow soldering operation (see, FIG. 4illustrating example solder reflow conditions). In particular, a solderpad 48 (e.g., a tin-lead, silver, gold, etc. plated copper pad, etc.) isprovided on the surface 42 of the PCB 44 (e.g., formed as part of thePCB 44, coupled to the PCB 44 by suitable operations, etc.), and thecontact 20 is initially coupled to the pad 48 via solder paste 50provided on the solder pad 48. The PCB 44 and contact 20 are thensubjected to a controlled heating process (e.g., in a reflow solderingoven of the reflow soldering operation, etc.) which melts the solderpaste 50 and permanently couples the contact 20 to the PCB 44. Duringthe reflow soldering operation, the contact 20 and PCB 44 are subjectedto various temperatures ranging from about 20 degrees Celsius (roomtemperature) up to about 280 degrees Celsius. With that said, it shouldbe appreciated that the components of the contact 20 (e.g., theresilient core member 22, the electrically conductive layer 26, theadhesive 24, etc.) are capable of withstanding these solder reflowconditions and the temperatures (and temperature changes) associatedtherewith (e.g., temperatures up to at least about 280 degrees Celsius,etc.). As such, the contact 20 can maintain its operational integrity(in terms of structure (e.g., without a bond between the adhesive 24,the resilient core member 22, and the electrically conductive layer 26failing; without the electrically conductive layer 26 opening orunwrapping; etc.), performance, etc.) following the reflow solderingoperation (e.g., the contact 20 is solder reflow processable, thecontact 20 is reflow tunnel compatible, etc.).

To allow the contact 20 to be surface mounted to the PCB 44 in theillustrated embodiment, the electrically conductive layer 26 is formedfrom material that can be soldered to the solder pad 48 (therebyallowing the contact 20 to be coupled to the PCB 44). In thisembodiment, the electrically conductive layer 26 comprises a metalizedpolyimide (PI) film layered (via a sputtering process) with acombination of copper and tin (e.g., a polyimide film plated with about56 percent copper and about 44 percent tin, a polyimide film plated withother percentages of copper and/or tin and/or other materials, etc.).The copper is provided on the polyimide film, and the tin is providedover the copper. The polyimide film may have any desired thickness(e.g., about 0.025 millimeters, greater than about 0.025 millimeters,less than about 0.025 millimeters, etc.); the copper may be provided ina layer having any desired thickness (e.g., about 0.00006 millimeters,greater than about 0.00006 millimeters, less than about 0.00006millimeters, etc.); and the tin may be provided in a layer having anydesired thickness (e.g., about 0.00004 millimeters, greater than about0.00004 millimeters, less than about 0.00004 millimeters, etc.).Generally, the copper provides electrical conductivity properties to thecontact 20 and the tin provides corrosion resistant properties to thecontact 20.

The resilient core member 22 of the illustrated embodiment is formedfrom a halogen-free foam product (e.g., a silicone foam product, apolyurethane foam product (e.g., SC60CH from The Woodbridge Group(Mississauga, Ontario, Canada), etc.), etc.). In some embodiments, theresilient core member 22 is formed from material (e.g., siliconematerial, silicone foam material, etc.) that is generally flameretardant. In other embodiments, the resilient core member 22 may beformed from material that is not flame rated and contains no flameretardant added thereto (the material contains no flame retardantadditives in the end product, and no flame retardant additives are addedprior or during the manufacture of the material) (e.g., the materialcontains no ammonium compounds, either added thereto prior or duringmanufacture or in the end product, etc.).

In the illustrated embodiment, the resilient core member 22 includes asilicone foam product having a density of about 15 pounds per cubicfoot. In other example embodiments, the resilient core member 22 mayinclude a silicone foam product having other densities (e.g., a densityof about 5 pounds per cubic foot or more (e.g., about 5 pounds per cubicfoot, about 5.6 pounds per cubic foot, about 6 pounds per cubic foot,about 7 pounds per cubic foot, etc.), etc.) within the scope of thepresent disclosure. This higher density silicone foam allows the contact20 to withstand higher temperatures, for example, without the coremember 22 melting (e.g., as may happen with foams having lower densities(e.g., densities of about 3.1 pounds per cubic foot or less, etc.). Inaddition, the silicone foam core member 22 of the illustrated embodimenthas very good thermal resistance and low compression set under hightemperature (e.g., temperatures associated with reflow soldering, etc.).The silicone foam core member 22 is also relatively soft (e.g., comparedto silicone rubber, etc.). As such, the illustrated contact 20, havingthe silicone foam core member 22, typically requires only slitting orcutting to provide desired dimensions, without requiring new molding.

And, the adhesive 24 of the illustrated embodiment includes asilicone-based adhesive (e.g., a silicone pressure sensitive adhesive,etc.). The silicone based adhesive can help facilitate bonding with thesilicone foam of the core member 22. In other embodiments, the adhesive24 may include an adhesive that is loaded with an effective amount offlame retardant (e.g., halogen-free flame retardant free of halogenssuch as bromines, chlorines, etc., etc.) to enable the contact 20 toachieve a UL-94 flame rating of V-0, while at the same time having goodbond strength and retaining properties suitable (e.g., bulk resistivity,etc.) for the desired contact applications. In still other embodiments,contacts may include adhesives such as solvent based polyesteradhesives, epoxy-based adhesives, hot melt adhesives, combinationsthereof, etc.

With that said, it should be appreciated that the present disclosure isnot limited to the particular electrically conductive film, foam core,and/or adhesive described in connection with the contact 20 of thisembodiment. Other materials may be used to make electrically conductivelayers, resilient core members, and/or adhesives in other embodiments.For example, the particular material(s) used for the electricallyconductive layers of the contacts may vary depending on the desiredelectrical properties (e.g., surface resistivity, electricalconductivity, etc.) and/or abrasion resistance, which, in turn, candepend, for example, on the particular application in which the contactswill be used. In addition, in other example embodiments, adhesives mayinclude flame retardants or, no flame retardants. Further, otheradhesives (e.g., epoxy-based adhesives, other polyurethane-basedadhesives, etc.) may be used.

The contact 20 of this embodiment is suitable for use with SMT processes(and is solder reflow processable), can achieve a flame rating of V-0under UL-94, is halogen free as defined by the IEC 61249-2-21 standard,and is RoHS compliant. In addition, example (non-limiting) properties ofthe illustrated contact 20 include a conductivity (surface resistance)of less than about 0.07 ohms per square, an adhesion power of soldering(e.g., a breakaway resistance, etc.) of greater than about 0.3kilogram-force, and a hardness (F type) of greater than about 80degrees. Further, the contact 20 provides almost no difference incompression ratio before and after soldering, and it is also softer andhas better force displacement resistance than some conventionalcontacts. A compression set of the contact 20 before exposure to thereflow soldering operation is less than about 10 percent, and acompression set of the contact 20 after exposure to the reflow solderingoperation is also less than about 10 percent (per ASTM D3574 (at 70degrees Celsius and 22 hours)). In addition, the contact 20 may be usedin shielding operations and may provide a shielding effectiveness of atleast about 80 decibels. And, a bond strength of the adhesive 24 of theillustrated contact 20 (to both the resilient core member 22 and theelectrically conductive layer 26) is at least about 0.05 newton permillimeter (about 5 ounces per inch).

FIG. 5 illustrates another example embodiment of a contact 120 suitablefor grounding and/or shielding functions and embodying one or moreaspects of the present disclosure. The contact 120 of this embodiment issimilar to the contact 20 previously described and illustrated inconnection with FIGS. 1-4. For example, the contact 120 includes aresilient core member 122, an electrically conductive layer 126generally surrounding the resilient core member 122, and a layer ofadhesive 124 bonding the electrically conductive layer 126 to theresilient core member 122. In addition, the contact 120 is compatiblewith SMT processes and, as desired, can be surface mounted to a surfaceof a PCB. Further, the contact 120 can achieve a flame rating of V-0under UL-94 (e.g., the adhesive 124 may include an effective amount offlame retardant such that the contact 120 has a UL-94 flame rating ofV-0, etc.), is halogen free as defined by the IEC 61249-2-21 standard,and is RoHS compliant. In this embodiment, though, the contact 120 has athickness 132 and width 134 defining a generally rectangular shape.

FIGS. 6 and 7 illustrate yet another example embodiment of a contact 220suitable for grounding and/or shielding functions and embodying one ormore aspects of the present disclosure. The contact 220 of thisembodiment is similar to the contact 20 previously described andillustrated in connection with FIGS. 1-4. For example, the contact 220includes a resilient core member 222, an electrically conductive layer226 generally surrounding the resilient core member 222, and a layer ofadhesive 224 bonding the electrically conductive layer 226 to theresilient core member 222. In addition, the contact 220 is compatiblewith SMT processes and, as desired, can be surface mounted to a surfaceof a PCB. Further, the contact 220 can achieve a flame rating of V-0under UL-94 (e.g., the adhesive 224 may include an effective amount offlame retardant such that the contact 220 has a UL-94 flame rating ofV-0, etc.), is halogen free as defined by the IEC 61249-2-21 standard,and is RoHS compliant.

In this embodiment, though, the contact 220 has a thickness 232 andwidth 234 defining a generally hourglass shape. The inventors hereofhave discovered that the contact 220, having the generally hourglassshape, deforms laterally inwardly (see arrows 254) at side portions 256of the contact 220 when a force (e.g., a compressing force, etc.) isapplied to a top portion 258 and/or a bottom portion 260 of the contact220 (e.g., compressing the contact 220 between the top and bottomportions 258, 260, etc.). As such, when installed to a PCB (e.g.,surface mounted to a surface of the PCB, etc.), the contact 220 does notinterfere with surrounding, adjacent components following application ofthe force to the contact 220 (and following subsequent compression ofthe contact 220), as compared to square shaped contacts, rectangularshaped contacts, etc. which may deform laterally outwardly at sideportions of the contacts when compressing forces are applied to topand/or bottom portions of the contacts. Thus, as compared to the squareshaped contacts, rectangular shaped contacts, etc. (which typicallyrequire larger clearances when installed to PCBs to avoid contact withnearby components, and possible electrical shorts, upon suchcompression), the hourglass shaped contact may be more suitable for usein smaller applications.

FIGS. 8 and 9 illustrate yet another example embodiment of a contact 320suitable for grounding and/or shielding functions and embodying one ormore aspects of the present disclosure. The contact 320 of thisembodiment is similar to the contact 20 previously described andillustrated in connection with FIGS. 1-4. For example, the contact 320includes a resilient core member 322, an electrically conductive layer326 generally surrounding the resilient core member 322, and a layer ofadhesive 324 bonding the electrically conductive layer 326 to theresilient core member 322. In addition, the contact 320 is compatiblewith SMT processes and, as desired, can be surface mounted to a surfaceof a PCB. Further, the contact 320 can achieve a flame rating of V-0under UL-94 (e.g., the adhesive 324 may include an effective amount offlame retardant such that the contact 320 has a UL-94 flame rating ofV-0, etc.), is halogen free as defined by the IEC 61249-2-21 standard,and is RoHS compliant.

In this embodiment, the contact 320 includes adhesive strips 370 (e.g.pressure sensitive adhesive (PSA) strips, conductive pressure sensitiveadhesive (CPSA) strips, etc.) located on a surface 372 (e.g., along abottom surface, along a seam side, etc.) of the contact 320. Theseadhesive strips 370 can be used to help hold the contact 320 in place ona PCB prior to, and in preparation for, the reflow soldering operation(e.g., against inadvertently moving, tipping, etc.). The adhesive strips370 can also be used to help ensure that the particular surface 372(e.g., the seam side, etc.) of the contact 320 is coupled to the surfaceof the PCB (thereby lessening the possibility of the contact 320 openingat the seam (e.g., lessening the possibility of the electricallyconductive layer 326 unwrapping, etc.) after exposure to heat). Whileadhesive strips 370 are provided in the illustrated embodiment, othershapes of the adhesive may be used.

The adhesive strips 370 can be located in any desired manner, fashion,orientation, etc. along the surface 372 of the contact 320, and canprovide coverage ranges anywhere from about 10 percent to about 100percent. When the adhesive strips 370 cover about 100 percent of thesurface 372 of the contact 320, CPSA strips may be used and relied uponfor desired electrical contact with a PCB, and soldering may beeliminated. When the adhesive strips 370 cover less than about 70percent of the surface 372 of the contact 370, PSA strips or CPSA stripsmay be used in combination with soldering for making desired electricalcontact with a PCB.

In addition, the adhesive strips 370 may include (e.g., may be filledwith, etc.) solder particles that can be used to permanently attach thecontact 320 to a PCB (following reflow soldering). Here, the adhesivestrips 370 with the solder particles can replace solder paste typicallyused when surface mounting the contact 320 to a PCB. The solderparticles can include materials suitable for soldering.

FIG. 10 illustrates another example embodiment of a contact 420 suitablefor grounding and/or shielding functions and embodying one or moreaspects of the present disclosure. The contact 420 of this embodiment issimilar to the contact 20 previously described and illustrated inconnection with FIGS. 1-4. For example, the contact 420 includes aresilient core member 422, an electrically conductive layer 426 (e.g., ametalized electrically conductive layer, etc.) generally surrounding theresilient core member 422, and a layer of adhesive 424 bonding theelectrically conductive layer 426 to the resilient core member 422. Inaddition, the contact 420 can achieve a flame rating of V-0 under UL-94(e.g., the adhesive 424 may include an effective amount of flameretardant such that the contact 420 has a UL-94 flame rating of V-0,etc.), is halogen free as defined by the IEC 61249-2-21 standard, and isRoHS compliant.

The contact 420 of this embodiment is also compatible with SMTprocesses. For example, a lower surface 446 of the contact 420 can besurface mounted to a surface 442 of a PCB 444 (as viewed in FIG. 10) forelectrically coupling the contact 420 to the PCB 444. As such, thecontact 420 can be used as a ground circuit of the PCB 444, for example,as part of a SMT process for constructing an electronic circuit, etc.The contact 420 may be placed on the surface 442 of the PCB 444 manuallyor via suitable pick and place equipment (e.g., a gripper, a pneumatichead, a vacuum pick-and-place head, a suction cup pick-and-place head,etc.). In the illustrated embodiment, the contact 420 is surface mountedto the PCB 444 via a soldering operation. In particular, a solder pad448 (e.g., a tin-lead, silver, gold, etc. plated copper pad, etc.) isprovided along the lower surface of the PCB 444 (e.g., formed as part ofthe PCB 444, coupled to the PCB 444 by suitable operations, etc.), andthe contact 420 is initially coupled to the pad 448 via solder paste 450provided on the solder pad 448. The PCB 444 and contact 420 are thensubjected to a controlled heating process (e.g., in a reflow solderingoven of a reflow soldering operation, etc.) which melts the solder paste450 and permanently couples the contact 420 to the PCB 444.

In this embodiment, the contact 420 includes a stiffener 476 locatedgenerally within the contact 420 and toward the lower surface 446 of thecontact 420 (as viewed in FIG. 10). The stiffener 476 operates toprovide a generally rigid structure to the contact 420 along theelectrically conductive layer 426. In addition, the stiffener 476 islocated between the electrically conductive layer 426 of the contact 420and the resilient core member 422. As such, the stiffener 476 alsoallows/accommodates compression of the resilient core member 422 duringinstillation, use, etc. of the contact 420, while helping maintain theoriginal configuration (e.g., shape, integrity, etc.) of the lowersurface 446 of the contact 420 (e.g., of the electrically conductivelayer 426 of the contact 420 coupled to the PCB 444, etc.).

With that said, use of the stiffener 476 may help inhibit cracking ofthe solder paste 450 that couples the contact 420 to the PCB 444. Suchcracking can result after the contact 420 is coupled to the PCB 444 andthe contact 420 is then compressed and/or moved (e.g., slid, etc.)during assembly or use (e.g., when other components engage the contact420, etc.). Such cracking can undesirably reduce conductivity of thecontact 420. As noted above, the stiffener 476 helps maintain theoriginal configuration (e.g., shape, integrity, etc.) of the lowersurface 446 of the contact 420 (e.g., of the electrically conductivelayer 426 of the contact 420 coupled to the PCB 444, etc.) when suchcompression of the resilient core member 422 occurs, thereby inhibitingoccurrence of this cracking of the solder paste 450. Use of thestiffener 476 may also help improve peel strength of the contact 420 andimprove durability of the contact 420.

In the illustrated embodiment, the stiffener 476 is formed from a resinmaterial. However, stiffeners could be formed from other suitablematerials within the scope of the present disclosure. Also in theillustrated embodiment, the stiffener 476 has a thickness dimension thatis greater than a corresponding thickness dimension of the solder paste450 coupling the contact 420 to the PCB 444. However, in other exampleembodiments, contacts may include stiffeners with other thicknessdimensions within the scope of the present disclosure.

FIG. 11 illustrates another example embodiment of a contact 520 suitablefor grounding and/or shielding functions and embodying one or moreaspects of the present disclosure. The contact 520 of this embodiment issimilar to the contact 20 previously described and illustrated inconnection with FIGS. 1-4. For example, the contact 520 includes aresilient core member 522, an electrically conductive layer 526 (e.g., ametalized electrically conductive layer, etc.) generally surrounding theresilient core member 522, and a layer of adhesive 524 bonding theelectrically conductive layer 526 to the resilient core member 522. Inaddition, the contact 520 can achieve a flame rating of V-0 under UL-94(e.g., the adhesive 524 may include an effective amount of flameretardant such that the contact 520 has a UL-94 flame rating of V-0,etc.), is halogen free as defined by the IEC 61249-2-21 standard, and isRoHS compliant.

The contact 520 of this embodiment is also compatible with SMTprocesses. For example, a lower surface 546 of the contact 520 can besurface mounted to a surface 542 of a PCB 544 (as viewed in FIG. 11) forelectrically coupling the contact 520 to the PCB 544. As such, thecontact 520 can be used as a ground circuit of the PCB 544, for example,as part of a SMT process for constructing an electronic circuit, etc.The contact 520 may be placed on the surface 542 of the PCB 544 manuallyor via suitable pick and place equipment (e.g., a gripper, a pneumatichead, a vacuum pick-and-place head, a suction cup pick-and-place head,etc.). In the illustrated embodiment, the contact 520 is surface mountedto the PCB 544 via a soldering operation. In particular, a solder pad548 (e.g., a tin-lead, silver, gold, etc. plated copper pad, etc.) isprovided along the lower surface of the PCB 544 (e.g., formed as part ofthe PCB 544, coupled to the PCB 544 by suitable operations, etc.), andthe contact 520 is initially coupled to the pad 548 via solder paste 550provided on the solder pad 548. The PCB 544 and contact 520 are thensubjected to a controlled heating process (e.g., in a reflow solderingoven of a reflow soldering operation, etc.) which melts the solder paste550 and permanently couples the contact 520 to the PCB 544.

In this embodiment, the contact 520 includes a plate 590 located outsideof the contact 520 and generally toward the lower surface 546 of thecontact 520 (as viewed in FIG. 11). The plate 590 is positionedgenerally between the contact 520 and the solder pad 548, and the plate590 is soldered to the contact 520 and the solder pad 548 when couplingthe contact 520 to the PCB 544. The plate 590 operates to provide agenerally rigid structure to the contact 520 along the electricallyconductive layer 526, and also separates the contact 520 from the solderpad 548. In the illustrated embodiment, the plate 590 includes multiplethrough holes (not visible) to allow the solder paste 550 flowtherethrough (from the solder pad 548) to help accommodate coupling thecontact 520 to the PCB 544.

With that said, use of the plate 590 may help inhibit cracking of thesolder paste 550 coupling the contact 520 to the PCB 544. Such crackingcan result after the contact 520 is coupled to the PCB 544 and thecontact 520 is then compressed and/or moved (e.g., slid, etc.) duringassembly or use (e.g., when other components engage the contact 520,etc.). Such cracking can undesirably reduce conductivity of the contact520. As noted above, the plate 590 provides a generally rigid structureto the contact 520 along the electrically conductive layer 526 andseparates the contact 520 from the solder pad 548. As such, compressionof the resilient core member 522 (and any associated movement of theelectrically conductive layer 526 along the lower surface 546 of thecontact 520) does not influence the solder paste 550 because it isseparated therefrom by the plate 590. Thus, occurrence of the crackingdescribed above of the solder paste 550 can be inhibited. Use of theplate 590 may also help improve peel strength of the contact 520 andimprove durability of the contact 520.

In the illustrated embodiment, the plate 590 is formed from a metalmaterial (e.g., a heat resistant metal material, etc.), and has athickness of about 0.1 millimeters. However, plates could be formed fromother suitable materials and/or could have other thickness dimensions(e.g., thickness dimensions of less than about 0.1 millimeters,thickness dimensions of greater than about 0.1 millimeters, thicknessdimensions between about 0.1 millimeters and about 0.15 millimeters,etc.) within the scope of the present disclosure.

EXAMPLES

The following examples are merely illustrative, and are not limiting tothe disclosure in any way.

Example 1

In this example, a flammability test per UL-94 was performed on anexample contact of the present disclosure. The contact included apolyether urethane foam core with a metallized tin/copper film bondedthereto by an adhesive. The metallized tin/copper film was formed by afully sputtering process and comprised a polyimide film having about56.25 percent copper and 43.75 percent tin.

In addition, in this example the polyether urethane foam used as thecore of the contact had the following properties. The foam was free ofhalogen containing flame retardants, and was free of any visiblewrinkles and creases. The foam had a tan color (comprising PANTONE 474C)and pore sizes of not more than 3.0 millimeters. The density of the foamwas between about 4.25 and about 4.75 pounds per cubic foot. Thehardness (F-type) of the foam was about 85 percent+/−5 percent. Theelongation of the foam was greater than about 80 percent. The tensilestrength of the foam was greater than about 15 pounds per square inch.The compression strength of the foam was between about 0.5 and 1.5pounds per square inch at about 50 percent compression. And, thecompression set of the foam (per ASTM D3574) was (1) less than about 10percent at 70 degrees Celsius, 22 hours, and 50% compression deflection,and (2) less than about 20 percent at 70 degrees Celsius, 168 hours, and50% compression deflection.

And, the adhesive included a solvent based polyurethane adhesive thatincluded about 52.3 percent of an aromatic polyester general purposeadhesive (having about 25 percent solids) (product 4849 from Henkel AG &Co. (Germany)), about 16.9 percent of a first fire retardant additive(product OP 935 from Clariant GmbH (Germany)), about 1.9 percent of asecond fire retardant additive (product FR CROS 489 from BudenheimIberica (Spain)), about 3.0 percent of an epoxy resin (product P-4 fromRoyce International (United States)) (in a 50 percent by weight blend ofToluene), and about 25.9 percent of toluene (to make the adhesive at asuitable viscosity (e.g., about 3,000 to 5,000 centipoise (cps)). Forthis adhesive, the percent solids in the dry film, after the solventsevaporate during drying, were about 39.17 percent of the general purposeadhesive, about 50.64 percent of the first fire retardant, about 5.69percent of the second fire retardant, and about 4.49 percent of theepoxy resin. A crosslinker was then added to the adhesive in thisexample to help improve temperature resistance.

To make the contact, the adhesive components were mixed together using asuitable laboratory mixer and then coated on silicone-treated releasepaper using a draw down bar (e.g., having a width dimension of about 10inches and a length dimension of about 8 inches, etc.) to make anadhesive coating (having a target weight of between about 3 ounces persquare yard and about 4 ounces per square yard). The adhesive coatingwas next dried at a temperature of about 100 degrees Celsius for about20 minutes to evaporate the toluene. A heat press was then used (at atemperature of about 350 degrees Fahrenheit for a duration of about 5seconds) to bond the adhesive to the metallized film. The sheets ofbonded adhesive and metallized film were then applied to foam core tomake the metallized film-over-foam contact for testing.

For the flammability test, five samples of the contact were made fortesting. Each of the samples had a thickness of about 3 millimeters. Theexample results of the flammability test are set forth in Table 2 (andare provided for purposes of illustration only). As indicated in Table2, the contact of this example achieved a UL-94 flame rating of V-0.

TABLE 2 Sample t₁ (s) t₂ (s) t₃ (s) Result 1 8.54 0 0 V-0 2 7.63 0 0 V-03 9.52 0 0 V-0 4 9.16 0 0 V-0 5 7.33 5 0 V-0 Total Afterflame = 42.18seconds UL-94 Flame Rating = V-0

Example 2

In this example, a flammability test per UL-94 was performed on anexample contact of the present disclosure. The contact included apolyether urethane foam core with a metallized tin/copper film bondedthereto by an adhesive. The polyether urethane foam core has the sameproperties as identified in Example 1. The metallized tin/copper filmwas again formed by a fully sputtering process and comprised a polyimidefilm having about 56.25 percent copper and 43.75 percent tin. And, theadhesive is the same as used in Example 1 (but without the crosslinkeradded).

For the flammability test, five samples of the contact were made fortesting. Each of the samples were approximately 3 millimeters thick, 13millimeters wide, and 125 millimeters long. The example results of theflammability test are set forth in Table 3 (and are provided forpurposes of illustration only). As indicated in Table 3, the contact ofthis example achieved a UL-94 flame rating of V-0.

TABLE 3 Sample t₁ (s) t₂ (s) t₃ (s) Result 1 2.85 5.16 0 V-0 2 7.29 3.040 V-0 3 2.44 2.24 0 V-0 4 7.90 1.32 0 V-0 5 4.72 3.61 0 V-0 TotalAfterflame = 40.57 seconds UL-94 Flame Rating = V-0

Example 3

In this example, a flammability test per UL-94 was performed on anexample contact of the present disclosure. The contact included apolyether urethane foam core with a metallized tin/copper film bondedthereto by an adhesive. The polyether urethane foam core has the sameproperties as identified in Example 1. The metallized tin/copper filmwas again formed by a fully sputtering process and comprised a polyimidefilm having about 56.25 percent copper and 43.75 percent tin. And, theadhesive is the same as used in Example 1 (but with a differentcrosslinker added).

For the flammability test, five samples of the contact were made fortesting. Each of the samples were approximately 3 millimeters thick. Theexample results of the flammability test are set forth in Table 4 (andare provided for purposes of illustration only). As indicated in Table4, the contact of this example achieved a UL-94 flame rating of V-1.

TABLE 4 Sample t₁ (s) t₂ (s) t₃ (s) Result 1 11.78 6.27 0 V-1 2 13.273.81 0 V-1 3 15.81 0 0 V-1 4 8.85 2.73 0 V-0 5 6.56 0 0 V-0 TotalAfterflame = 69.08 seconds UL-94 Flame Rating = V-1

Example 4

In this example, a flammability test per UL-94 was performed on anexample contact of the present disclosure. The contact included apolyether urethane foam core with a metallized tin/copper film bondedthereto by an adhesive. The polyether urethane foam core has the sameproperties as identified in Example 1. The metallized tin/copper filmwas again formed by a fully sputtering process and comprised a polyimidefilm having about 56.25 percent copper and 43.75 percent tin. And, theadhesive is the same as used in Example 3.

For the flammability test, five samples of the contact were made fortesting. Each of the samples were approximately 5 millimeters thick. Theexample results of the flammability test are set forth in Table 5 (andare provided for purposes of illustration only). As indicated in Table5, the contact of this example achieved a UL-94 flame rating of V-1.

TABLE 5 Sample t₁ (s) t₂ (s) t₃ (s) Result 1 23.94 0 0 V-1 2 15.62 2.350 V-1 3 19.30 5.67 0 V-1 4 17.26 0 0 V-1 5 18.91 0 0 V-1 TotalAfterflame = 103.05 seconds UL-94 Flame Rating = V-1

Example 5

In this example, a flammability test per UL-94 was performed on anexample contact of the present disclosure. The contact included apolyether urethane foam core with a metallized tin/copper film bondedthereto by an adhesive. The polyether urethane foam core has the sameproperties as identified in Example 1. The metallized tin/copper filmwas again formed by a fully sputtering process and comprised a polyimidefilm having about 56.25 percent copper and 43.75 percent tin. And, theadhesive is the same as used in Example 1 (but without the crosslinkeradded thereto).

For the flammability test, three samples of the contact were made fortesting each having a 3 millimeter thickness. Three samples of thecontact were made for testing each having a 5 millimeter thickness. And,three samples of the contact were made for testing each having a 10millimeter thickness. The example results of the flammability test areset forth in Tables 6-8 (and are provided for purposes of illustrationonly). As indicated in Tables 6-8, the contacts of this example, at eachof the thicknesses of 3 millimeters, 5 millimeters, and 10 millimeters,achieved a UL-94 flame rating of HB. As a note, the abbreviation “NBTL”in the Burn Rate column of the tables stands for “not burned to line”,which is an automatic pass for the horizontal burn test.

TABLE 6 Sample (3 mm) Burn Rate (mm/min) Result 1 NBTL Pass 2 NBTL Pass3 NBTL Pass

TABLE 7 Sample (5 mm) Burn Rate (mm/min) Result 1 NBTL Pass 2 NBTL Pass3 NBTL Pass

TABLE 8 Sample (10 mm) Burn Rate (mm/min) Result 1 NBTL Pass 2 NBTL Pass3 NBTL Pass

Example 6

In this example, a Restriction of Hazardous Substances (RoHS) test wasperformed on an example contact of the present disclosure. The contactincluded a polyether urethane foam core with a metallized tin/copperfilm bonded thereto by adhesive. The polyether urethane foam core hasthe same properties as identified in Example 2. And, the metallizedtin/copper film was again formed by a fully sputtering process andcomprised a polyimide film having about 56.25 percent copper and 43.75percent tin.

For the RoHS test, the contact was analyzed for various metals,polybrominated biphenyls (PBBs), polybrominated diphenyl ethers (PBDEs),and halogens (see, Table 9). Inductively coupled plasma atomic emissionspectroscopy (ICP-AES) was used for detecting cadmium, lead, andmercury. Ultraviolet-visible spectroscopy (UV-VIS) was used fordetecting hexavalent chromium. Gas chromatography-mass spectrometry(GC-MS) was used for detecting the PBBs and the PBDEs. And, ionchromatography (IC) was used for detecting fluorine, chlorine, andbromine. The example results of the RoHS test are shown in Table 4 (andare provided for purposes of illustration only). As indicated by theTest Result “ND” (no detection) in the Table 9, none of the test itemswere detected using the above testing methods (ICP-AES, UV-VIS, GC-MS,and IC) and their given method detection limits (“MDL”). Accordingly,none of the items listed in Table 9 were detected in the contact,indicating that the contact is RoHS compliant (as well as halogen freeper IEC 61249-2-21). Note that in Table 9 for the method detectionlimits (“MDL”), 1 milligram per kilogram (mg/kg) is equal to 1 part permillion (1 ppm).

TABLE 9 Test Item Test Result MDL Cadmium ND 2 mg/kg Lead ND 2 mg/kgMercury ND 2 mg/kg Hexavalent Chromium ND 2 mg/kg Sum of PBBs ND —Monobromobiphenyl ND 5 mg/kg Dibromobiphenyl ND 5 mg/kg TribromobiphenylND 5 mg/kg Tetrabromobiphenyl ND 5 mg/kg Pentabromobiphenyl ND 5 mg/kgHexabromobiphenyl ND 5 mg/kg Heptabromobiphenyl ND 5 mg/kgOctabromobiphenyl ND 5 mg/kg Nonabromobiphenyl ND 5 mg/kgDecabromobiphenyl ND 5 mg/kg Sum of PBDEs ND — Monobromodiphenyl etherND 5 mg/kg Dibromodiphenyl ether ND 5 mg/kg Tribromodiphenyl ether ND 5mg/kg Tetrabromodiphenyl ether ND 5 mg/kg Pentabromodiphenyl ether ND 5mg/kg Hexabromodiphenyl ether ND 5 mg/kg Heptabromodiphenyl ether ND 5mg/kg Octabromodiphenyl ether ND 5 mg/kg Nonabromodiphenyl ether ND 5mg/kg Decabromodiphenyl ether ND 5 mg/kg Fluorine ND 50 mg/kg  ChlorineND 50 mg/kg  Bromine ND 50 mg/kg 

Example 7

In this example, a force/displacement/electrical resistance test wereperformed on an example contact of the present disclosure. The contactwas sized with a thickness of about 7 millimeters and a width of about 7millimeters. The results of the test are shown in FIG. 12.

Example 8

In this example, force/displacement/electrical resistance tests wereperformed on two different shapes of an example contact of the presentdisclosure. The two different shapes of the contact evaluated includedone having a generally square cross-sectional shape (such as the shapeof contact 20 illustrated in FIG. 1) and one having a generallyhourglass cross-sectional shape (such as the shape of the contact 220illustrated in FIG. 6).

The example contacts (used for evaluating both shapes) each included apolyether urethane foam core (such as the one described in Example 2)with a metallized tin/copper film bonded thereto by adhesive. Again, themetallized tin/copper film was formed by a fully sputtering process andcomprised a polyimide film having about 56.25 percent copper and 43.75percent tin.

In a first set of force displacement and electrical resistance tests,the two different shaped contacts were both approximately 5 millimetersthick, 5 millimeters wide, and 5 millimeters long. In a second set offorce displacement and electrical resistance tests, the two differentshaped contacts were both approximately 5 millimeters thick, 10millimeters wide, and 5 millimeters long. And, in a third set of forcedisplacement and electrical resistance tests, the two different shapedcontacts were both approximately 10 millimeters thick, 10 millimeterswide, and 10 millimeters long.

The results of the tests are shown in FIGS. 13-15. FIG. 13 illustratesthe results of the first set of tests, FIG. 14 illustrate the results ofthe second set of tests, and FIG. 15 illustrates the results of thethird set of tests. Lines 480 the results for the square shaped contact,and lines 482 illustrate the results for hourglass shaped contact.Generally, in each of the tests, the electrical resistance of thehourglass shaped contact was greater than that of the square shapedcontact, while the force displacement for both shapes of the contactswere substantially similar.

Example 9

In this example, a compression set test, a force/displacement/electricalresistance test, and a flammability test per UL-94 were performed on anexample contact of the present disclosure. The contact included asilicone foam core with a metallized tin/copper film bonded thereto by avulcanized silicone adhesive. The metallized tin/copper film was againformed by a fully sputtering process and comprised a polyimide filmhaving about 56.25 percent copper and 43.75 percent tin. The contact hada thickness of about 13 millimeters, a width of about 13 millimeters,and a length of about 13 millimeters. And, the tests were performed onthe contact after two exposures to a reflow soldering operation (see,e.g., FIG. 4, etc.).

The compression set test was performed on five samples of the finishedcontact in accordance with ASTM D3574, modified to 125° C. The resultsof the compression set test are shown in Table 10 (and are provided forpurposes of illustration only). As can be seen, the compression set foreach sample was less than 10 percent. And, the results of theforce/displacement/electrical resistance test are shown in FIG. 16 (andare provided for purposes of illustration only). For the flammabilitytest, five samples of the contact were made for testing. The exampleresults of the flammability test are set forth in Table 11 (and areprovided for purposes of illustration only). As indicated, the contactof this example achieved a UL-94 flame rating of V-0.

TABLE 10 Compression 50% Original Thickness (30 min) 13.19 13.11 13.1213.29 13.22 (mm) Thickness after 125° C., 22 hrs 12.68 12.64 12.6 12.9112.54 (mm) Compression Set (%) 3.87 3.59 3.96 2.86 5.14 AverageCompression Set (%) 3.88

TABLE 11 Sample t₁ (s) t₂ (s) t₃ (s) Result 1 0.98 1.02 0 V-0 2 1.121.82 0 V-0 3 0 2.10 0 V-0 4 0.84 2.31 0 V-0 5 0 1.16 0 V-0 TotalAfterflame = 11.35 seconds UL-94 Flame Rating = V-0

Example 10

In this example, a flammability test per UL-94 was performed on anexample contact of the present disclosure. The contact included asilicone foam core with a metallized tin/copper film bonded thereto by avulcanized silicone adhesive. The metallized tin/copper film was againformed by a fully sputtering process and comprised a polyimide filmhaving about 56.25 percent copper and 43.75 percent tin. The contact hada thickness of about 3 millimeters, a width of about 3 millimeters, anda length of about 3 millimeters. And, the tests were performed on thecontact after two exposures to a reflow soldering operation (see, e.g.,FIG. 4, etc.). The example results of the flammability test are setforth in Table 12 (and are provided for purposes of illustration only).As indicated, the contact of this example achieved a UL-94 flame ratingof V-1.

TABLE 12 Sample t₁ (s) t₂ (s) t₃ (s) Result 1 10.09 3.49 0 V-1 2 13.42 00 V-1 3 12.24 3.48 0 V-1 4 8.78 4.21 0 V-0 5 10.79 2.85 0 V-1 TotalAfterflame = 69.35 seconds UL-94 Flame Rating = V-1

With that said, it should be appreciated that a wide range of materialscan be used for the resilient core members, the electrically conductivelayers, and the adhesives of the contacts of the present disclosure. Byway of example, the resilient core members, the electrically conductivelayers, and/or the adhesives of the present disclosure may comprise oneor more corresponding materials disclosed in United States PatentApplication Publication US2010/0258344 published Oct. 14, 2010, thedisclosure of which is incorporated herein by reference in its entirety.

In some example embodiments, the resilient core member may be made of afoam material (e.g., a silicone foam material, a polymeric elastomermaterial, a cellular polymeric foam such as an open celled foam, aclosed cell foam, a urethane foam (e.g., a polyester foam, a polyetherfoam, a combination thereof, etc.), a polyurethane foam, etc.), asilicone rubber material, etc. And, a scrim (e.g., a polyester scrim,etc.) may be attached to the resilient core member as desired.

In some example embodiments, the resilient core member may comprise afoam material having a compression set (per ASTM D3574 (test D)) of lessthan about 15% and/or a density of between about 3 pounds per cubic footand about 7 pounds per cubic foot (e.g., between about 3.5 pounds percubic foot and about 4.2 pounds per cubic foot, about 5.6 pounds percubic foot, etc.). In one specific example, a resilient core member maybe formed from a halogen-free polyurethane foam product available fromThe Woodbridge Group (Mississauga, Ontario, Canada) (e.g., productSC60CH, etc.), etc. Here, the foam product used is not flame rated andhas the following physical properties: a density of about 3.5 to about4.2 pounds per cubic foot; a 25% Indentation Force Deflection (IFD) ofabout 60 to about 80 pounds per 50 square inches; a charcoal color;contains no flame retardant (the foam product contains no flameretardant additives in the end product, and no flame retardant additivesare added prior or during the manufacture of the foam product) (e.g.,the foam product contains no ammonium compounds, either added theretoprior or during manufacture or in the end product, etc.); a tearstrength of at least about 0.8 pounds per inch; a tensile strength of atleast about 12 pounds per square inch; and an elongation (at break) ofabout 100%. In addition, the foam product used to form the resilientcore member is a polyester that is die clickable.

In some example embodiments, the resilient core member may comprise asilicone foam material having a compression set (per ASTM D3574 (testD)) of less than about 15% and/or a density of greater than about 5pounds per cubic foot (e.g., about 5.6 pounds per cubic foot, about 6pounds per cubic foot, about 7 pounds per cubic foot, etc.).

In some example embodiments, the resilient core member may not include(and may be free of) any flame retardant (and may not have any addedthereto at any time), for example, either during the process of makingthe resilient core member or in the final product of the resilient coremember used in the example contacts. For example, the resilient coremember may not be flame rated, the resilient core member may includeless than about 1,000 parts per million of flame retardant, theresilient core member may include undetectable amounts of flameretardant, the resilient core member may include a de minimis or trivialamount of flame retardant; etc. In other example embodiments, theresilient core member may be entirely free of flame retardants.

In some example embodiments, the resilient core member (e.g., a foammaterial of the resilient core member, etc.) may not include (and may befree of, and may not have added thereto at any time) any ammoniumcompounds (e.g., ammonium carbonate, etc.), chlorine, bromine, antimony,compounds thereof, etc. either during the process of making theresilient core member or in the final product of the resilient coremember used in the example contacts. And, such example embodiments ofthe contacts may be able to achieve flame ratings of V-0 under UL-94(without having any flame retardant added to or present in the resilientcore member at any time). This is a significant accomplishment giventhat presence of flame retardant inside a core member (and particularlyinside a foam core member) can tend to decrease the core member'sperformance in compression set and compression load deflection tests.

In some example embodiments, the resilient core member may be provided(e.g., applied, coated, impregnated, mixed, plated, vapor deposited,fabricated, formed, combinations thereof, etc.) with flame retardants(e.g., halogen-free flame retardants, etc.). For example, variousembodiments may include a resilient core member provided with halogenfree flame retardant such that the resilient core member is able toachieve a flame rating under UL-94 of HF-1.

In some example embodiments, the resilient core member may have adensity of at least about 3 pounds per cubic foot or more (e.g., about 3pounds per cubic foot, about 3.1 pounds per cubic foot, about 3.5 poundsper cubic foot, about 4 pounds per cubic foot, about 5 pounds per cubicfoot, about 5.6 pounds per cubic foot, etc.). For example, using a foamproduct for a resilient core member having a density of at least about3.5 pounds per cubic foot provides a better compression set than a lessdense foam material (e.g., a foam material having a density of about 3pounds per cubic foot or less, etc.). But it is noted that in exampleembodiments where the resilient core member is made from urethane foam,flammability of the resilient core member may increase as the density ofthe resilient core member increases (e.g., a resilient core memberhaving a density of about 4 pounds per cubic foot may be more flammablethan a resilient core member having a density of about 3 pounds percubic foot, etc.). Thus, it may become more difficult to achieve higherflame ratings (e.g., flame ratings of V-0 under UL-94, etc.) forcontacts when using such a higher density urethane foam resilient coremember (e.g., a urethane foam resilient core member having a density ofabout 4 pounds per cubic foot or more, etc.).

In some example embodiments, the electrically conductive layer may havea conductivity (or surface resistivity) of less than about 0.20 ohms persquare after at least about 1,000 hours of exposure of the contacts madefrom the electrically conductive layer to a substantially constanttemperature of at least about 40 degrees Celsius and a substantiallyconstant relative humidity of at least about 90%. In other exampleembodiments, the electrically conductive layer may have a conductivityof less than about 0.07 ohms per square (e.g., about 0.04 ohms persquare, about 0.03 ohms per square, etc.) under similar conditions.

In some example embodiments, the electrically conductive layer canprovide fire resistance to the contacts.

In some example embodiments, the adhesive may include environmentallysafe adhesives suitable for providing good bond strength between theelectrically conductive layer and the resilient core member. Theadhesive can be formed into a layer and then laminated in production ofthe contacts (e.g., fusion laminated to the electrically conductivelayer, etc.).

In some example embodiments, the adhesive may include any of a widerange of flame retardants, including environmentally friendly flameretardants that are halogen free (e.g., free of halogens such asbromines, chlorines, etc.). Halogen-free flame retardants used inconnection with the contacts and the adhesive thereof may include, forexample, phosphorous-based flame retardants, etc. Particular examples ofcommercially available halogen-free phosphorous-based flame retardantsare sold by Apex Chemical Company (Spartanburg, S.C.). Other exampleflame retardants that can be used include mineral oxides (e.g.,magnesium hydroxide, antimony oxide, etc.), metal hydrates (e.g.,aluminum trihydrate, etc.) boron compounds (e.g., boric acid, borax,etc.), melamines, silicones, etc.

In some example embodiments, the adhesive includes at least an effectiveamount of halogen-free flame retardant to achieve a predetermined flamerating. Alternatively, the adhesive can also include more than thateffective amount. For example, the adhesive may include less than apredetermined percentage by dry weight of halogen-free flame retardant,below which percentage the adhesive provides at least a predeterminedbond strength. It should be appreciated that there is a delicate balancethat should be maintained with the halogen-free flame retardant and theadhesive. If the adhesive contains too much halogen-free flameretardant, the bond strength can be compromised. But if the adhesivedoes not include enough halogen-free flame retardant, then the contactsmay not be able to meet the desired UL-94 flame rating (e.g., V-0, V-1,V-2, HB, HF-1, etc.). Accordingly, in one particular embodiment, anadhesive includes at least an effective amount of halogen-free flameretardant for providing a contact with a UL-94 flame rating of V-0, butless than a predetermined percentage below which the adhesive providesat least a sufficient bond strength for maintaining integrity of thecontact (e.g., at least 4 ounces per inch width as determined bystandard testing, for example, such as a 90 degree peel at 12 inches perminute, etc.). The various numerical ranges disclosed herein defineacceptable balances between flame resistance (using halogen-free flameretardants) and adhesive bond strength to provide contacts that have anadhesive with adequate bond strength and adequate flame resistance(using halogen-free flame retardants), for example, to achieve flameratings of V-0 under UL-94.

In some example embodiments, the adhesive (e.g., defining an adhesivelayer, etc.) comprises a thermoplastic polyurethane resin. In some ofthese example embodiments, the adhesive may comprise about 25% to about60% by dry weight (e.g., about 30% by dry weight, about 50% by dryweight, about 55% by dry weight, etc.) of the thermoplastic polyurethaneresin (e.g., with flame retardant making up the rest of the adhesive,etc.). In some example embodiments, the adhesive may include an amountof halogen-free flame retardant of at least about 30% (+/− about 5%) butnot more than about 70% by dry weight. Or, the adhesive may include anamount of halogen-free flame retardant of at least about 50% but notmore than about 63% by dry weight. Or, the adhesive may include anamount of halogen-free flame retardant of at least about 54.5% to about67.3% by dry weight. Or, the adhesive may include an amount ofhalogen-free flame retardant of about 63% by dry weight. Or, theadhesive may include an amount of halogen-free flame retardant of about55% by dry weight. Or, the adhesive may include an amount ofhalogen-free flame retardant of about 50% by dry weight.

In some example embodiments, the adhesive may be loaded (e.g.,fabricated, formed, mixed, etc.) with an effective amount ofhalogen-free flame retardant (e.g., more than about 30% by dry weight,about 30% to about 70%, about 40% to about 67% by dry weight, about54.5% to about 63% by dry weight, about 45% to about 56% by dry weight,about 50% by dry weight, about 55% by dry weight, etc.), which mayenable the contacts to achieve a predetermined flame retardant rating(e.g., a UL-94 flame rating of V-0, etc.). In some of these exampleembodiments, the contacts may include an adhesive loaded with aneffective amount of halogen-free flame retardant in combination withhalogen-free flame retardant provided to the resilient core member,thereby allowing the contacts to achieve a predetermined flame retardantrating (e.g., a UL-94 flame rating of V-0, etc.) while still beinghalogen free. In other ones of these example embodiments, the contactsmay include an adhesive loaded with an effective amount of halogen-freeflame retardant such that the contacts can achieve a predetermined flameretardant rating (e.g., a UL 94 flame rating of V-0, etc.) without flameretardant being provided to the resilient core member thereof.

In some example embodiments, the effective amount of halogen-free flameretardant in the adhesive is less than a predetermined percentage belowwhich the loaded adhesive provides at least a predetermined bondstrength (e.g., at least about 10 ounces per inch width as determined,for example, by a 90 degree peel (or T-peel) test at 12 inches perminute, etc.). Thus, it should be appreciated that if too little flameretardant is included in the adhesive, flame resistance will beinsufficient. And, if too much flame retardant is included in theadhesive, bond strength will be insufficient. As described herein, abalance has been found between flame resistance and bond strength. Inaddition to the amount of flame retardant in the adhesive, the bondstrength of the adhesive may also depend on the particular substrate towhich it is bonding.

In some example embodiments, the adhesive may include a thermoplasticpolyurethane composite resin composition loaded with halogen-free flameretardant instead of halogen-based flame retardant (such that theadhesive does not include halogenated flame retardants), instead ofexpandable carbon graphite (ECG) flame retardants, and/or instead of redphosphorous flame retardants (e.g., which can be detected using amicroscope, etc.). For example, the adhesive may include halogen-freephosphorous-based flame retardants that do not include ECG or redphosphorus flame retardants. As such, in these example embodiments theadhesive may be viewed as being free of (and not including) halogen (andhalogen-based flame retardants), ECG, and/or red phosphorus. Contactsincluding such an adhesive may advantageously be capable of achievingUL-94 flame ratings of V-0, and may be able to avoid undesirable effectsoften associated with red phosphorous flame retardants and/or with ECGflame retardants. Notably when used in adhesives in contacts, redphosphorus may cause corrosion in the contacts and ECG, which is anelectrically conductive material, may cause undesirable electricalshorts inside electronic devices.

In some example embodiments, the adhesive (the adhesive layer definedthereby) may have a thicknesses (e.g., an average thickness, a generallyuniform thickness, etc.) of less than about 1 millimeter (e.g., about0.5 millimeters or less, etc.). In some of these example embodiments,the adhesive layer may have thicknesses of about 0.1 millimeters or less(e.g., about 0.09 millimeters, about 0.06 millimeters, etc.).

In some example embodiments, the adhesive may define a single layer ofmaterial. For example, in these example embodiments the adhesive mayinclude halogen-free flame retardant mixed therein such that theadhesive and the halogen-free flame retardant together define a singlelayer of material. Contacts including the example adhesive may be ableto achieve flame ratings of V-0 under UL-94 (e.g., without having anyflame retardant added to or present in the resilient core member at anytime, etc.). By providing the halogen-free flame retardant to theadhesive in such a manner (so that the adhesive and halogen-free flameretardant define a single layer of material), multiple different layersof material (e.g., a first layer of adhesive and a second, separatelayer of flame retardant covering the adhesive, etc.) are not required,for example, to achieve a desired flame rating (e.g., a flame rating ofV-0 under UL-94, etc.). As such, the adhesive and halogen-free flameretardant defining a single layer of material may provide cost savingswhen used to make the contacts, improved ease in making the contacts,etc. Previously in the art, such multiple different layers of materialwere used to achieve desired flame ratings in contacts while avoidingproblems associated with losing adhesive strength when the flameretardant was mixed into the adhesive.

In some example embodiments, the adhesive may include a solvent-basedadhesive. For example, the adhesive may include a thermoplasticpolyurethane resin composition (having flame retardant particles mixedtherein) made via a wet coating process, where the adhesive is coatedonto release paper. Here, a solvent (e.g., toluene, ethyl acetate,water, etc.) may be used to keep the adhesive liquid for coating priorto drying. But after the adhesive dries in a thin film form (e.g., in alayer between a resilient core member and an electrically conductivelayer, where the adhesive layer may have a thickness of about 1millimeter or less (e.g., about 0.09 millimeters, about 0.06millimeters, etc.), etc.), the solvent evaporates leaving behind thethermoplastic polyurethane resin composition with the flame retardantparticles mixed in. The amount of solvent remaining in the adhesive thatdidn't evaporate is very small (e.g., less than about 0.1%, etc.). Usingthis solvent based wet coating process may lead to better/higheradhesive bond strengths and also may allow for production of very thinadhesive layers (e.g., layers having thicknesses of about 1 millimeteror less (e.g., about 0.09 millimeters, about 0.06 millimeters, etc.),etc.) with enough halogen-free free flame retardant therein to allowcontacts to achieve UL-94 flame ratings of V-0, even when that contactsdo not include flame retardant additives in the foam and/or do notinclude ECG flame retardants, halogenated flame retardants, or redphosphorous flame retardants. It is noted that while the solvent mayinclude water (e.g., such that the adhesive may include a water-basedadhesive, etc.), solvents such as toluene, ethyl acetate, etc. may allowfor more efficient manufacturing of the contacts, as water tends to takelonger to evaporate during manufacture than do other solvents such astoluene, ethyl acetate, etc.

In some example embodiments, the adhesive may be prepared using suitabledevices capable, for example, of effectively dispersing the flameretardant particles within the adhesive at a temperature greater than amelting point of the adhesive to thereby prepare the mixture of theadhesive and the flame retardant particles.

In some example embodiments, the adhesive may include a thermoplasticpolyurethane resin composition made via an extrusion process withoutsolvent and requiring no release paper.

In some example embodiments, the adhesive may also include at least oneor more additives such as antioxidants, stabilizers, lubricants,reinforcing agents, pigments, colorants, plasticizers, etc. Theadditives may be included in the adhesive layers in desired amounts (orranges of amounts) so as to not reduce bond strength and/or flameresistance of the adhesive layers.

In some example embodiments, two or more different kinds of adhesivesmay be used to define an adhesive layer of a contact.

Any suitable flame retardants may be used in connection with contacts ofthe present disclosure. Example flame retardants may includephosphorous-based flame retardants (e.g., organic phosphorus compounds,phosphinates (e.g., Exolit OP, etc.), diphosphinates, polymers thereof,cyclic phosphonate ester blends, combinations thereof, etc.), nitrogencompounds, ammonium compounds, mineral oxides (e.g., magnesiumhydroxide, etc.), metal hydrates (e.g., aluminum trihydrate, etc.),boron compounds (e.g., boric acid, borax, etc.), melamine derivatives(e.g., melamines, melamine cyanurate, melamine phosphate, melaminepolyphosphate, melamine borate, etc.), neoprenes, silicones,combinations thereof, etc.

Phosphorus flame retardants may interrupt decomposition in a condensedphase and may increase char yield during combustion, while providingflame retardancy, for example, to the contacts. For example, whenphosphorus flame retardants are added to the adhesive used in contacts,the adhesive may provide flame retardancy to the contacts (particularlyin contacts where the adhesive comprises a resin with high oxygencontent, such as thermoplastic polyurethane resin). Here, the chargenerally includes a layer of carbonized resin caused by combustion. Theformation of char helps inhibit spreading of fire through the contacts.

Example embodiments of the contacts may include combinations of flameretardants, additives, other compounds, etc. Such combinations mayprovide improved flame retardancy (e.g., may provide an expandable charlayer through a synergy effect of the different flame retardants tothereby inhibiting the spread of oxygen and heat, etc.).

In some example embodiments, the contacts may include an adhesivecomprising phosphorous flame retardants in combination with melaminederivatives and nitrogen compounds. Here, use of the phosphorous flameretardants in combination with the nitrogen compounds can promotegeneration of phosphoric acid amide through combustion, which forms anexpandable char layer with increased thickness (thereby inhibitingtransfer of heat and oxygen required for combustion).

Example embodiments of the contacts may include adhesives comprisingflame retardants (e.g., halogen-free flame retardants, etc.) havingdesired particle sizes. Particle sizes of flame retardants may influencephysical properties of the adhesive layers. For example, flameretardants with smaller particle sizes may provide improved physicalproperties and flame retardancy to the adhesive layers (e.g., largerparticle sizes may inhibit dispersion within the adhesive layers, etc.).In some of these example embodiments, the flame retardants havingparticle sizes between about 1 micrometer and about 60 micrometers (andmore preferably between about 1 micrometer and about 20 micrometers).

Following are various example adhesives suitable for use with thecontacts of the present disclosure. One example adhesive includes athree component mixture, comprising 998 HS (a solvent based polyurethaneadhesive product (having about 53% solids) made by DSM NeoSol Inc. (EastProvidence, R.I.)), AP-422 (a flame retardant ammonium polyphosphate(APP) product (having about 100% solids) made by Clariant GmbH(Germany)), and toluene (a solvent used to disperse the AP-422 and lowerviscosity of the mixture). The mixture of this example included about 75grams (or about 53% by wet weight) of 998HS, about 36 grams (or about26% by wet weight) of AP-422, and about 30 grams (or about 21% by wetweight) of toluene. As such, the mixture had a dry weight percentage of998HS of about 52.5%, a dry weight percentage of AP-422 of about 47.5%,a viscosity of about 8,280 centipoise, and a weight pick-up of about4.20 opsy.

Another example adhesive includes a three component mixture, comprising138-293C (a urethane adhesive product (having about 38% solids) made byDSM NeoSol Inc.), AP-462 (a flame retardant ammonium polyphosphate (APP)product (having about 100% solids) made by Clariant GmbH made fromAP-422 by micro-encapsulation with melamine resin), and toluene (asolvent used to disperse the AP-462 and lower viscosity of the mixture).The mixture of this example included about 89 grams (or about 52% by wetweight) of 138-293C, about 50 grams (or about 29% by wet weight) ofAP-462, and about 33 grams (or about 19% by wet weight) of toluene. Assuch, the mixture had a dry weight percentage of 138-293C of about40.3%, a dry weight percentage of AP-462 of about 59.6%, a viscosity ofabout 2,580 centipoise, and a weight pick-up of about 3.62 opsy.

Another example adhesive includes a four component mixture, comprising138-293C (a urethane adhesive product (having about 38% solids) made byDSM NeoSol Inc.), AP-462 (a flame retardant ammonium polyphosphate (APP)product (having about 100% solids) made by Clariant GmbH made fromAP-422 by micro-encapsulation with melamine resin), toluene (a solventused to disperse the AP-462 and lower viscosity of the mixture), andPCMLE 828 (an epoxy resin product made by Polochema (Taipei, Taiwan)used to improve adhesion of 138-293C). The mixture of this exampleincluded about 89 grams (or about 50% by wet weight) of 138-293C, about50 grams (or about 28% by wet weight) of AP-462, about 33 grams (orabout 19% by wet weight) of toluene, and about 6 grams of PCMLE 828 (orabout 3% by wet weight). As such, the mixture had a dry weightpercentage of 138-293C of about 37.6%, a dry weight percentage of AP-462of about 55.7%, a dry weight percentage of PCMLE 828 of about 6.7%, aviscosity of about 2,520 centipoise, and a weight pick-up of about 3.7opsy.

Another example adhesive includes a three component mixture, comprising138-293C (a urethane adhesive product (having about 38% solids) made byDSM NeoSol Inc.), AP-462 (a flame retardant ammonium polyphosphate (APP)product (having about 100% solids) made by Clariant GmbH made fromAP-422 by micro-encapsulation with melamine resin), and toluene (asolvent used to disperse the AP-462 and lower viscosity of the mixture).The mixture of this example included about 85 grams (or about 49% by wetweight) of 138-293C, about 55 grams (or about 32% by wet weight) ofAP-462, and about 33 grams (or about 19% by wet weight) of toluene. Assuch, the mixture had a dry weight percentage of 138-293C of about 37%,a dry weight percentage of AP-462 of about 63%, and a viscosity of about2,070 centipoise.

Another example adhesive includes a four component mixture, comprising144-122 (a solvent based urethane adhesive product (with a solidscontent of about 28%) made by DSM NeoSol Inc.), OP-935 (a fine-grainedorganic phosphinate flame retardant product (having about 100% solids)made by Clariant GmbH), FR CROS 489 (a special grade ammoniumpolyphosphate (APP) product (having about 100% solids) coated withmelamine and made by Budenheim Iberica (Germany)), PCMLE 828 (an epoxyresin product made by Polochema (Taipei, Taiwan), ED 5121 (a colorantproduct made by Cardinal Color, Inc. (Paterson, N.J.)), and toluene (asolvent used to disperse the FR CROS 489 and lower viscosity of themixture). The mixture of this example included about 88 grams (or about52% by wet weight) of 144-122, about 28 grams (or about 16.7% by wetweight) of OP-935, about 3.5 grams (or about 2.1% by wet weight) of FRCROS 489, about 13 g (or about 7.7% by wet weight) of PCMLE 828, about0.3 grams of ED 5121 (or about 0.5% by wet weight), and about 35 grams(or about 21% by wet weight) of toluene. As such, the mixture had a dryweight percentage of 144-122 of about 35.6%, a combined dry weightpercentage of OP-935 and FR CROS 489 of about 45.6%, and a dry weightpercentage of PCMLE 828 of about 18.8%. In addition, the mixture had aviscosity of about 1,500 centipoise and a weight pick-up of about 2.28opsy.

Another example adhesive includes a four component mixture, comprisingDispercoll 8758 (a water based polyurethane adhesive product (having asolids content of about 40%) made by Bayer MaterialScience (Pittsburgh,Pa.)), AP-422 (a flame retardant ammonium polyphosphate (APP) product(having about 100% solids) made by Clariant GmbH), Rheolate-2000 (arheology modifier made by Elementis Specialties Inc. (Highstown, N.J.)),and water (a solvent used to disperse the AP-422 and lower the viscosityof the mixture). The mixture of this example included about 208 grams(or about 54% by wet weight) of Dispercoll 8758, about 96 grams (orabout 25% by wet weight) of AP-422, about 4 grams (or about 1% by wetweight) of Rheolate-2000, and about 80 grams (or about 20% by wetweight) of water. As such, the mixture had a dry weight percentage ofDispercoll 8758 of about 46.1%, a dry weight percentage of AP-422 ofabout 53.3%, and a dry weight percentage of Rheolate-2000 of about 0.6%.In addition, the mixture had a viscosity of about 13,740 centipoise anda weight pick-up of about 3.4 opsy.

In some example embodiments, contacts may have trapezoid cross-sectionalshapes. In these embodiments, lower surfaces of the contacts may begenerally flat for installation to printed circuit boards, and thetrapezoidal shapes may reduce interference of the contacts with otheritems on the printed circuit boards.

Example embodiments are provided so that this disclosure will bethorough, and will fully convey the scope to those who are skilled inthe art. Numerous specific details are set forth such as examples ofspecific components, devices, and methods, to provide a thoroughunderstanding of embodiments of the present disclosure. It will beapparent to those skilled in the art that specific details need not beemployed, that example embodiments may be embodied in many differentforms, and that neither should be construed to limit the scope of thedisclosure. In some example embodiments, well-known processes,well-known device structures, and well-known technologies are notdescribed in detail. In addition, advantages and improvements that maybe achieved with one or more example embodiments of the presentdisclosure are provided for purpose of illustration only and do notlimit the scope of the present disclosure, as example embodimentsdisclosed herein may provide all or none of the above mentionedadvantages and improvements and still fall within the scope of thepresent disclosure.

Specific dimensions, specific materials, and/or specific shapesdisclosed herein are example in nature and do not limit the scope of thepresent disclosure. The disclosure herein of particular values andparticular ranges of values for given parameters are not exclusive ofother values and ranges of values that may be useful in one or more ofthe examples disclosed herein. Moreover, it is envisioned that any twoparticular values for a specific parameter stated herein may define theendpoints of a range of values that may be suitable for the givenparameter (i.e., the disclosure of a first value and a second value fora given parameter can be interpreted as disclosing that any valuebetween the first and second values could also be employed for the givenparameter). Similarly, it is envisioned that disclosure of two or moreranges of values for a parameter (whether such ranges are nested,overlapping or distinct) subsume all possible combination of ranges forthe value that might be claimed using endpoints of the disclosed ranges.

The terminology used herein is for the purpose of describing particularexample embodiments only and is not intended to be limiting. As usedherein, the singular forms “a”, “an” and “the” may be intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. The terms “comprises,” “comprising,” “including,” and“having,” are inclusive and therefore specify the presence of statedfeatures, integers, steps, operations, elements, and/or components, butdo not preclude the presence or addition of one or more other features,integers, steps, operations, elements, components, and/or groupsthereof. The method steps, processes, and operations described hereinare not to be construed as necessarily requiring their performance inthe particular order discussed or illustrated, unless specificallyidentified as an order of performance. It is also to be understood thatadditional or alternative steps may be employed.

When an element or layer is referred to as being “on”, “engaged to”,“connected to” or “coupled to” another element or layer, it may bedirectly on, engaged, connected or coupled to the other element orlayer, or intervening elements or layers may be present. In contrast,when an element is referred to as being “directly on,” “directly engagedto”, “directly connected to” or “directly coupled to” another element orlayer, there may be no intervening elements or layers present. Otherwords used to describe the relationship between elements should beinterpreted in a like fashion (e.g., “between” versus “directlybetween,” “adjacent” versus “directly adjacent,” etc.). As used herein,the term “and/or” includes any and all combinations of one or more ofthe associated listed items. The term “about” when applied to valuesindicates that the calculation or the measurement allows some slightimprecision in the value (with some approach to exactness in the value;approximately or reasonably close to the value; nearly). If, for somereason, the imprecision provided by “about” is not otherwise understoodin the art with this ordinary meaning, then “about” as used hereinindicates at least variations that may arise from ordinary methods ofmeasuring or using such parameters. For example, the terms “generally”,“about”, and “substantially” may be used herein to mean withinmanufacturing tolerances.

Although the terms first, second, third, etc. may be used herein todescribe various elements, components, regions, layers and/or sections,these elements, components, regions, layers and/or sections should notbe limited by these terms. These terms may be only used to distinguishone element, component, region, layer or section from another region,layer or section. Terms such as “first,” “second,” and other numericalterms when used herein do not imply a sequence or order unless clearlyindicated by the context. Thus, a first element, component, region,layer or section could be termed a second element, component, region,layer or section without departing from the teachings of the exampleembodiments.

Spatially relative terms, such as “inner,” “outer,” “beneath”, “below”,“lower”, “above”, “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. Spatiallyrelative terms may be intended to encompass different orientations ofthe device in use or operation in addition to the orientation depictedin the figures. For example, if the device in the figures is turnedover, elements described as “below” or “beneath” other elements orfeatures would then be oriented “above” the other elements or features.Thus, the example term “below” can encompass both an orientation ofabove and below. The device may be otherwise oriented (rotated 90degrees or at other orientations) and the spatially relative descriptorsused herein interpreted accordingly.

The foregoing description of the embodiments has been provided forpurposes of illustration and description. It is not intended to beexhaustive or to limit the disclosure. Individual elements, intended orstated uses, or features of a particular embodiment are generally notlimited to that particular embodiment, but, where applicable, areinterchangeable and can be used in a selected embodiment, even if notspecifically shown or described. The same may also be varied in manyways. Such variations are not to be regarded as a departure from thedisclosure, and all such modifications are intended to be includedwithin the scope of the disclosure.

What is claimed is:
 1. A contact for circuit grounding of surface mounttechnology devices, the contact comprising: a resilient core member; asolderable electrically conductive layer including a metallized film;and an adhesive bonding the solderable electrically conductive layer tothe resilient core member, the adhesive having no more than a maximum of900 parts per million chlorine, no more than a maximum of 900 parts permillion bromine, and no more than a maximum of 1,500 parts per milliontotal halogens; whereby the contact is solderable to a surface of aprinted circuit board.
 2. The contact of claim 1, wherein: the resilientcore member comprises foam; the solderable electrically conductive layerincludes a metallized polyimide film; the contact has no more than amaximum of 900 parts per million chlorine, no more than a maximum of 900parts per million bromine, and no more than a maximum of 1,500 parts permillion total halogens; and the contact has a flame rating of V-0 underUnderwriter's Laboratories (UL) Standard No.
 94. 3. The contact of claim2, wherein the contact is able to withstand solder reflow conditions andtemperatures up to at least about 280 degrees Celsius and maintainoperational structural integrity following a solder reflow operation. 4.The contact of claim 1, wherein the contact has a flame rating of V-0under Underwriter's Laboratories (UL) Standard No.
 94. 5. The contact ofclaim 1, wherein the contact has a flame rating of V-1, V-2, or HB underUnderwriter's Laboratories (UL) Standard No.
 94. 6. The contact of claim1, wherein the solderable electrically conductive layer includes ametallized polyimide film.
 7. The contact of claim 1, wherein thecontact has no more than a maximum of 900 parts per million chlorine, nomore than a maximum of 900 parts per million bromine, and no more than amaximum of 1,500 parts per million total halogens.
 8. The contact ofclaim 1, wherein the contact is able to withstand solder reflowconditions and temperatures and maintain operational structuralintegrity following a solder reflow operation.
 9. A halogen-free contactfor circuit grounding of surface mount technology devices, the contactcomprising: a resilient core member; a metal composition filmsurrounding at least part of the resilient core member and that issolderable; and an adhesive bonding the metal composition film to theresilient core member; wherein the resilient core member, the metalcomposition film, and the adhesive combined have no more than a maximumof 900 parts per million chlorine, no more than a maximum of 900 partsper million bromine, and no more than a maximum of 1,500 parts permillion total halogens such that the contact is halogen free; andwherein the contact has a flame rating of V-0 under Underwriter'sLaboratories (UL) Standard No. 94; whereby the contact is solderable toa surface of a printed circuit board.
 10. The contact of claim 9,wherein: the resilient core member comprises foam; the metal compositionfilm includes a metallized polyimide film; and the contact is able towithstand solder reflow conditions and temperatures up to at least about280 degrees Celsius and maintain operational structural integrityfollowing a solder reflow operation.
 11. The contact of claim 10,wherein the foam comprises silicone foam, and/or wherein the foam has adensity of about 15 pounds per cubic foot or more.
 12. The contact ofclaim 9, wherein the metal composition film includes a metallizedpolyimide film.
 13. The contact of claim 9, wherein the contact is ableto withstand solder reflow conditions and temperatures and maintainoperational structural integrity following a solder reflow operation.14. A method of installing a flame retardant, halogen free contact to asurface of a printed circuit board, the contact including a resilientcore and a metallized film surrounding at least part of the resilientcore, the method comprising soldering the metallized film of the halogenfree contact to a surface of a printed circuit board, whereby anelectrical pathway is established from the printed circuit board to thecontact through the metallized film, wherein the contact has no morethan a maximum of 900 parts per million chlorine, no more than a maximumof 900 parts per million bromine, and no more than a maximum of 1,500parts per million total halogens.
 15. The method of claim 14, wherein:the resilient core comprises foam; the metallized film includes ametallized polyimide film; and the contact has a flame rating of V-0under Underwriter's Laboratories (UL) Standard No.
 94. 16. The method ofclaim 14, further comprising placing the contact using a surface mounttechnology machine onto a ground trace of the printed circuit board,wherein the ground trace is pre-screened with solder paste.
 17. Themethod of claim 14, further comprising performing a solder reflowoperation while the contact is on the solder paste to thereby solder thecontact to the ground trace of the printed circuit board.
 18. The methodof claim 14, wherein the contact has a flame rating of V-0 underUnderwriter's Laboratories (UL) Standard No.
 94. 19. The method of claim14, wherein the contact has a flame rating of V-1, V-2, or HB underUnderwriter's Laboratories (UL) Standard No.
 94. 20. The method of claim14, wherein the contact is able to withstand solder reflow conditionsand temperatures and maintain operational structural integrity followinga solder reflow operation.